Roh'lix^® Operating Characteristics

Efficiency
The rolling contact between the outer races of the six ball bearings and the driveshaft provides a smooth, quiet linear motion, resulting in a minimum of 90% efficiency.

Backlash
Roh'lix bearings are preloaded by the coil springs to reduce backlash to less than 0.001 inch, which help maintain consistency throughout the life of the bearings.

Positioning Accuracy
The Roh'lix is a friction drive device and as a result, will show an accumulated error that is, in general, up to 0.002 inches per shaft revolution. Where greater accuracy is required, linear encoders can be used to indicate position.

Overload Protection The Roh'lix has the ability to slip if an obstruction is encountered in the system. This unique advantage over other types of linear actuators can prevent damage and costly downtime.

Lubrication
Roh'lix bearings are factory-lubricated for life and are designed to run on a clean, non-lubricated driveshaft.

Shafting
Recommended driveshaft material is C-1060 hardened and ground shafting with a minimum hardness of HRC 58. Its hardness will provide optimum life expectancy and its ground surface provides a uniform friction surface. Stainless steel shafting, although slightly softer, is adequate for many applications requiring corrosion protection.

Temperature
Acceptable temperature range is -10°F to +180°F. Special units available for higher or lower temperatures.

Maintenance
Unit is maintenance free, however, the shafting may require occasional wiping to clean off foreign matter that may accumulate.

Backdriving
By applying a thrust load to the Roh'lix unit, the shaft can be made to rotate. The thrust load will cause the Roh'lix and any device attached to it to travel along the shaft. Therefore, the Roh'lix should never be relied upon as the sole device to hold position.

Tandem Roh'lix
Two Roh'lix may be used on a common shaft in series, or in parallel on separate shafts, however, the combined thrust rating must be derated by 20%. When installing the Roh'lix units, be sure to tighten the thrust adjustment screws an equal number of turns so that they share the thrust load equally.

Roh'lix Life Expectancy
Roh'lix lifetime can range anywhere from 2 million to over 100 million inches of linear travel, depending on the application variables. The following factors should be considered to maximize the lifetime of Roh'lix:

• Thrust: Roh'lix lifetime is increased when the application thrust load is a smaller percentage of the unit's thrust rating. Selecting an oversized Roh'lix is advisable to achieve the greatest lifetime of the unit.
• Lead/Shaft Speed: Higher lead units will produce longer lifetime because fewer bearing revolutions will be required to move the same linear distance as a low lead unit. Also, reductions in the driveshaft RPM will increase lifetime. For a given linear speed, a higher lead will allow a lower shaft speed, and the two factors in combination will work to yield a greater lifetime.
• Overloading: Occasional slippage for short periods of time is acceptable. However, frequent or extended periods of slippage will result in reduced lifetime of the bearings.
• Other: Minimize sideloads and twisting loads to gain maximum life from the Roh'lix.

Loading
The Roh'lix is intended for axial loading. Sideloads and twisting loads (Figure 1) should be avoided whenever possible, as they cause uneven bearing loading and shorten lifetime.

Figure 1

Whenever possible, the load weight on the Roh'lix should be supported by a separate linear bearing assembly. Where sideloads cannot be avoided, the amount of the sideload should be subtracted from the thrust capacity of the unit. The amount of the sideload should never exceed 50% of the actuator's thrust capacity. If necessary, select an oversized Roh'lix to handle these application conditions.

Installation
The Roh'lix has a split-block for ease of installation. The two block halves can be assembled around the shaft, eliminating the need for removal of pillow-block bearings, coupling, etc. The split-block design is also a benefit for removal of the Roh'lix for service, such as bearing replacement.

Thrust Adjustment
Thrust of the Roh'lix is set by one of three methods:

• Adjust the thrust adjustment screws in increasing amounts until thrust setting is enough to carry load without slipping. This allows slippage before an overload builds up an unnecessary thrust load causing reduced bearing life.
• Use a spring scale to set the amount of thrust This technique works where the thrust requirement is known.
• Use the thrust per turn rating (Figure 2) to determine the appropriate number of turns of the thrust adjustment screws. This technique also works where the thrust requirement is known.

To set a given thrust on the Roh'lix, start with the thrust adjustment screws loose, then tighten by hand until the screw head lightly touches the top of the spring. Tighten both adjusting screws one full turn.This will set the thrust as shown in the thrust column of Figure 2. Finish the thrust adjustment by turning the additional turns as necessary.